The present invention relates to tin-silver coatings to be applied to substrate materials used in electrical and electronic applications, such as in automotive connectors, and to a method of applying a tin-silver coating to the substrate materials.
Electrical contacts in automobiles are subjected to a variety of hazards because of the elevated temperatures and environment in which they must function. For example, automotive electrical contacts are routinely subjected to vibrations and fretting corrosion caused by micromotion. Fretting corrosion is a detriment because it elevates contact resistance at the contacts of the electrical surface. Additionally, electrical arcing can occur when two electrical contacts or terminals are mated together.
To deal with some of these problems, some automotive electrical contacts have been coated with gold. Gold is an advantageous material because it does not lead to the production of deleterious oxides. The cost of gold however is very high and unduly increases the cost of the automotive electrical contact.
To eliminate the expense of the gold, some electrical contacts have been coated with pure tin. While economically beneficial, a pure tin coating does not have a very long cycle life, normally about 170 cycles.
Thus, there remains a need for a coating which can be used in the formation of electrical contacts which is economically beneficial and which can withstand the stresses of the environment under which automotive electrical contacts must function.